Origin of beach-stranded tars from source rocks indigenous to Seychelles

Black, malleable tar is 3-5 times as abundant as brownish-black hard tar stranded or beached on Mahe Island whereas only soft tar occurs on Coetivy Island. Malleable tar is characterized by abundant norhopane and tricyclic terpanes, low diasterane, lack of oleanane and bicadinane, and significant sulphur suggests a pre-late Cretaceous carbonate source. Hard tar is characterized by abundant diasteranes and tricyclic terpanes, and minor oleanane and bicadinane suggests a late Cretaceous clastic source with some interbedded carbonate. The soft tar consists of abundant pristane and tricyclic terpanes, and minor steranes, oleanane, bicadinane, and botryococcane suggest derivation from a late Cretaceous clastic deltaic source. These tars appear to be locally sourced.